A newly discovered nucleotide/nucleoside slavage pathway for the biosynthesis of NAD will be completely characterized in the bacterium Salmonella typhimurium. Previously uncharacterized structural and regulatory genes are being identified by both genetic and biochemical criteria. In eukaryotic cells, the mitochondrial NAD biosynthesis will be characterized. The enzymology of the enzyme poly ADP-ribose synthase will be investigated, and microinjection studies to characterize NAD and poly ADP-ribose will be continued.